537 research outputs found

    ATLAS jet and missing-ET reconstruction, calibration, and performance

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    AbstractThe ATLAS experiment has achieved a very high precision on jet and missing transverse energy performance by the use of advanced calorimeter-based topological clustering and local cluster calibration, event-by-event pile-up subtraction methods, and in situ techniques to correct for the residual jet energy response difference between data and simulation. Tracking information is being combined with calorimeter to further improve the jet and missing transverse energy performance. ATLAS has also commissioned several new powerful tools for the analysis and interpretation of hadronic final states at the LHC such as jet substructure, jet mass, quark-gluon discrimination, and jet tagging tools for the identification of boosted heavy particles. An overview of the reconstruction, calibration, and performance of jets, missing transverse energy, jet substructure, and jet tagging at ATLAS is presented

    Particle-level pileup subtraction for jets and jet shapes

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    We present an extension to the jet area-based pileup subtraction for both jet kinematics and jet shapes. A particle-level approach is explored whereby the jet constituents are corrected or removed using an extension of the methods currently being employed by the LHC experiments. Several jet shapes and nominal jet radii are used to assess the performance in simulated events with pileup levels equivalent to approximately 30 and 100 interactions per bunch crossing, which are characteristic of both the LHC Run I and Run II conditions. An improved performance in removing the pileup contributions is found when using the new subtraction method. The performance of the new procedure is also compared to other existing methods

    Erarbeitung von Schwellenwerten zur gezielten Bekämpfung von Zwergsteinbrand (Tilletia controversa) und Steinbrand (Tilletia caries) sowie deren praktische Umsetzung im Öko- Landbau

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    Dwarf bunt of wheat (Tilletia controversa) and common bunt of wheat (Tilletia caries) are the most important pathogens in organic cereal production. The aim of this research work is to find out whether a threshold value for seed is sufficient or whether the infection potential in the soil must be considered additionally. For dwarf bunt of wheat two-years-lasting field trials are performed at 3 sites with susceptible and low-susceptible wheat and spelt cultivars, 4 infection levels and 4 replications. The field trials are designed in a randomized split-block design with additional marginal-plots, so (1) sowing and harvest will be possible without greater interaction between the field plots, (2) spore contamination of the soil during harvest will be assured and (3) the determination of spore inoculum density in the soil after harvest will be enabled. Only fields with natural spore contamination are chosen. The field trials for common bunt of wheat are carried out in a similar design with 4 replicates at 4 sites with susceptible and low-susceptible wheat cultivars and two different sowing times. For an infestation with dwarf bunt of wheat, diffuse light is sufficient. The wheat cultivar Capo showed a significantly lower infestation than the cultivar Saturnus. The infestation of the spelt cultivar Franckenkorn was significantly lower than that of the cultivar Oberkulmer Rotkorn, with the infestation of spelt cultivars being in principle lower because of morphological features. The greatest significant number of infested spikes per m² was found in the variant soil infection. With the dwarf bunt of wheat results from the first year no threshold values can be determined neither for seed nor for soil. In the case of infestation with common bunt of wheat, there were no significant differences between the early and late sowing dates, nor between the cultivars Capo and Tommi. The highest bunt spore potential in the soil was found at the field trial site in Saxony; however, the highest number of infested spikes per m² was not found there

    Efficient numerical method to handle boundary conditions in 2D elastic media

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    A numerical method is developed to efficiently calculate the stress (and displacement) field in finite 2D rectangular media. The solution is expanded on a function basis with elements that satisfy the Navier-Cauchy equation. The obtained solution approximates the boundary conditions with their finite Fourier series. The method is capable to handle Dirichlet, Neumann and mixed boundary value problems as well and it was found to converge exponentially fast to the analytical solution with respect to the size of the basis. Possible application in discrete dislocation dynamics simulations is discussed and compared to the widely used finite element methods: it was found that the new method is superior in terms of computational complexity.Comment: 21 pages, 10 figure

    Schwellenwerte und weitere Entscheidungshilfen bei Befall mit Zwergsteinbrand (Tilletia controversa) und Steinbrand (Tilletia caries)

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    Beim Zwergsteinbrand zeigte sich, dass bei günstigen Infektionsbedingungen bereits ca. 50 Sporen in 10 g Boden zu einem starken Befall am Erntegut führen. Bei den verwendeten Sorten konnten keine nennenswerten Unterschiede im Befall festgestellt werden. Ein Schwellenwert von 20 Sporen/Korn ist nach den derzeitigen Ergebnissen auch für Zwergsteinbrand ausreichend. Da ein Abschätzen der Winterwitterung schwer möglich ist, wäre ein Grenzwert für das Infektionspotenzial im Boden, vor der Weizen- oder Dinkelsaat, durchaus überlegenswert. Dieser lässt sich aber nach einem einjährigem hohen Befall noch nicht festlegen. Der Steinbrandbefall ist stark von den Auflaufbedingungen abhängig. Nach zwei vorliegenden Versuchsjahren hat sich gezeigt, dass neben einer gezielten Sortenwahl und einen späten Saattermin (Ende Oktober) der Befall am Erntegut gering gehalten werden kann. Es konnte auch nachgewiesen werden, dass die Infektion vom Boden erfolgt. Zur Aussaat sollte nur Z-Saatgut verwendet werden, denn je höher das ausgesäte Saatgut bereits mit Brandsporen befallen ist, umso höher ist der Befall im nächsten Jahr beim Erntegut. Ziel des Weizenanbaus muss sein, das Sporenpotenzial im Boden und am Erntegut so gering wie möglich zu halten. Für einen Grenzwert im Boden besteht derzeit keine Notwendigkeit, da einem Befall mit entsprechender Sortenwahl und späten Saattermin entgegengewirkt werden kann

    Zkoumání vlastností top kvarku pomocí experimentu ATLAS na LHC

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    Tato disertační práce prezentuje měření diferenciálního účinného průřezu produkce párů kvarků top-antitop ve srážkách protonů s těžišťovou energií 8 TeV na experimentu ATLAS. Toto měření je provedeno pomocí událostí top-antitop v rozpadovém kanálu s jedním nabitým leptonem pro top kvarky s vysokou příční hybností. Měřený diferenciální účinný průřez je vyjádřen jako funkce příční hybnosti top kvarku na částicové a partonové úrovni. Změřená spektra jsou v souhlasu s předpovědí Standardního Modelu. V práci jsou popsané ex- perimentální metody používané pro toto měření s důrazem na rekonstrukci jetů a identifikace jetů pocházejících z fragmentace b-kvarků. Rekonstrukce jetů je ovlivněna srážkami více protonů (pileup) a je studováno potlačení těchto efektů. Je navržen nový způsob na odstranění pileup efektů, který je založen na metodách v současnosti používaných na LHC experimentech. Tato nová metoda účinně opravuje jety na úrovni jejich konstituentů. 1This thesis presents the measurement of the differential cross section of the top-antitop pair production in proton-proton collisions at center-of-mass energy of 8 TeV at the ATLAS experiment. The measurement is performed for top-antitop events in the single lepton decay channel in the boosted topol- ogy. The measured differential cross section is expressed as a function of the top quark transverse momentum at particle level and at parton level. The mea- sured distributions are compatible with the theoretical predictions of the Standard Model. The experimental techniques used in this measurement are discussed with emphasis on the jet reconstruction and on the identification of jets originating from b-quark fragmentation. The jet reconstruction is influenced by simultane- ous proton-proton collisions (pileup), and the mitigation of these pileup effects is studied. A novel pileup subtraction technique for jets is proposed using an ex- tension of the methods currently being employed by the LHC experiments. The new method has a good performance in removing the pileup contributions at the level of jet constituents. 1Ústav částicové a jaderné fyzikyInstitute of Particle and Nuclear PhysicsMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

    Workload balancing in distributed virtual reality environments

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    Virtual Reality (VR) has grown to become state-of-theart technology in many business- and consumer oriented E-Commerce applications. One of the major design challenges of VR environments is the placement of the rendering process. The rendering process converts the abstract description of a scene as contained in an object database to an image. This process is usually done at the client side like in VRML [1] a technology that requires the client’s computational power for smooth rendering. The vision of VR is also strongly connected to the issue of Quality of Service (QoS) as the perceived realism is subject to an interactive frame rate ranging from 10 to 30 frames-per-second (fps), real-time feedback mechanisms and realistic image quality. These requirements overwhelm traditional home computers or even high sophisticated graphical workstations over their limits. Our work therefore introduces an approach for a distributed rendering architecture that gracefully balances the workload between the client and a clusterbased server. We believe that a distributed rendering approach as described in this paper has three major benefits: It reduces the clients workload, it decreases the network traffic and it allows to re-use already rendered scenes

    Evaluation of a field-test kit for triazine herbicides (SensioScreen® TR500) as a fast assay to detect pesticide contamination in water samples

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    11 pages, 3 figures, 7 tables.-- Available online Nov 16, 2002.A field-test kit (SensioScreen® TR500) for the determination of triazine herbicides in water samples has been evaluated. The test is based on an ELISA method performed on a membrane that allows the visual estimation of the presence of triazine herbicides in <10 min. The kit contains all necessary reagents and equipment, and operates on a very simple protocol. The detection level of this semiquantitative kit has been set at 0.5 μg/l (for the sum of all triazines), although concentration levels of 0.1 μg/l for atrazine can be detected. This is the first time that a commercial field-test kit to control water contamination by herbicides performs in compliance with the EU and USA legislations regarding the limit of detection reached. Evaluation and validation studies have been performed using spiked, certified (AquaCheck) and real environmental samples comparing the results with chromatographic methods. In spite of the semiquantitative–qualitative character of the kit, the results demonstrate that the test SensioScreen® TR500 provides a very good estimation of the atrazine concentration in the sample. This test format could be adapted to the detection of other contaminants of environmental relevance.This work has been supported by CICYT (BIO2000-0351-P4-05) and by INIA (VIN0053-C3).Peer reviewe

    Quantifying the Transit Light Source Effect: Measurements of Spot Temperature and Coverage on the Photosphere of AU Microscopii with High-Resolution Spectroscopy and Multi-Color Photometry

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    AU Mic is an active 24 Myr pre-main sequence M dwarf in the stellar neighborhood (d==9.7 pc) with a rotation period of 4.86 days. The two transiting planets orbiting AU Mic, AU Mic b and c, are warm sub-Neptunes on 8.5 and 18.9 day periods and are targets of interest for atmospheric observations of young planets. Here we study AU Mic's unocculted starspots using ground-based photometry and spectra in order to complement current and future transmission spectroscopy of its planets. We gathered multi-color LCO 0.4m SBIG photometry to study the star's rotational modulations and LCO NRES high-resolution spectra to measure the different spectral components within the integrated spectrum of the star, parameterized by 3 spectral components and their coverage fractions. We find AU Mic's surface has at least 2 spectral components, a 4000±154000\pm15 K ambient photosphere with cool spots that have a temperature of 3000±703000\pm70 K and cover 39±4%39\pm4\% percent of the surface, increasing and decreasing by 5%\% from the average throughout a rotation. We also detect a third flux component with a filling factor less than 0.5%\% and a largely uncertain temperature that we attribute to flare flux not entirely omitted in the time-averaged spectra. We include measurements of spot temperature and coverage fraction from both 2- and 3- temperature models, which we find agree with each other strongly. Our expanded use of various techniques to study starspots will help us better understand this system and may have applications for interpreting the transmission spectra for exoplanets transiting stars of a wide range of activity levels.Comment: 25 pages, 13 figures, Accepted to Ap
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